The cone spindle of a blade transmitter, which measures consistency of pulp slurry, is typically designed to bend in an over load condition. The purpose of the bending is to protect bearings and other internal parts of the blade transmitter. On the other hand, the bending has a negative effect on accuracy of the consistency measurements. Furthermore, it is impossible to know whether the cone spindle has bent or not without detaching the blade transmitter from the process pipe and performing a visual checking. The checking is undesirable because it requires a stoppage of the process operation. A similar problem exists also when other kind of viscometers such as a rotating consistency meter are used. Hence, there is a need to improve the checking.